Submersible transport canister and methods for the use thereof

ABSTRACT

Embodiments of a submersible transport canister, and embodiments of using a submersible transport canister, are provided. In one embodiment, the submersible transport canister includes a pressure vessel having a storage cavity configured to store at least one item therein, a cap movable to a closed position wherein the cap sealingly engages the pressure vessel, and a diver-adjustable buoyancy system configured to be coupled to the pressure vessel. When coupled to the pressure vessel, the diver-adjustable buoyancy system is configured to displace a volume of water to achieve a substantially neutral buoyancy during underwater transport of the item within the submersible transport canister.

TECHNICAL FIELD

The following disclosure relates generally to submersible devices and, more particularly, to embodiments of a submersible transport canister having a diver-adjustable buoyancy system for the underwater transport of non-marinized items, as well as to methods for utilizing such a canister.

BACKGROUND

The term “marinized” is commonly utilized to describe items that have been engineered to withstand direct and prolonged exposure to harsh marine environments during, for example, underwater transport by a military or civilian diver. Marinized versions of many different items have been developed and are commercially available, including different types of tools and electronic devices (e.g., flashlights). Although many different marinized items are commercially available, such items tend to be relatively costly as compared to their non-marinized, commercial-off-the-shelf counterparts. In addition, marinized versions of certain items are generally not available due to excessive cost or difficulties encountered in marinizing the item. As a specific example, high-energy-density batteries often have chemistries (e.g., lithium ion chemistries) that react adversely with saltwater and are consequently difficult to marinize without encasing such batteries within a watertight package, which can add undesirable cost, bulk, and weight to the marinized battery.

Relatively simple, submersible containers have long been commercially available that can be carried on a diver's person and utilized to store non-marinized items, such as mobile phones or other electronic devices, during recreational dives. Such submersible containers are generally capable of providing a watertight seal to moderate depths and, in a general sense, can be utilized for the underwater transport of one or more non-marinized items. However, when closed, such submersible containers typically do not allow the passage of gas into or out of the container's storage cavity. As a result, such conventional submersible containers are generally unsuitable for the transport of combustible items, such as lithium ion batteries, which may burn in a failure state. Furthermore, such conventional submersible containers typically do not provide a means for allowing the diver to adjust the container's buoyancy to compensate for the items or items carried by the container. Consequently, when submerged and carrying one or more items, a conventional submersible container may be either lighter or heavier than the volume of water displaced by the container. The submerged container consequently exerts a net upward force or downward force on the diver, which the diver must overcome to maintain a desired depth. While this may be acceptable for a civilian diver during a relatively short or shallow dive, carrying or manually towing a container that continually tends to sink or rise can be inconvenient for a civilian diver during longer, deeper dives or for a military diver equipped with additional gear and possibly operating in adverse maritime conditions (e.g., low ambient light, Sea States approaching or exceeding Code 3, etc.). This may also render such conventional submersible containers unsuitable for usage during Hurricane Disaster Water Recovery, Boat Accident Recovery, and similar disaster or accident recovery efforts.

It is thus desirable to provide embodiments of a submersible transport canister that can be utilized by a diver to transport non-marinized, commercial-off-the-shelf items, including lithium ion batteries and other combustible items. It would also be desirable if embodiments of the submersible transport canister included a diver-adjustable buoyancy system, which can be adjusted by the diver to compensate for the weight of the item or items stored within the canister to achieve a substantially neutral buoyancy and thereby facilitate diver transport of the loaded canister. Finally, it would be describable for embodiments of such a submersible transport canister to be scalable, reliable, and relatively inexpensive to produce. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and this Background.

BRIEF SUMMARY

Embodiments of a submersible transport canister, and embodiments of using a submersible transport canister, are provided. In one embodiment, the submersible transport canister includes a pressure vessel having a storage cavity configured to store at least one item therein, a cap movable to a closed position wherein the cap sealingly engages the pressure vessel, and a diver-adjustable buoyancy system configured to be coupled to the pressure vessel. When coupled to the pressure vessel, the diver-adjustable buoyancy system is configured to displace a volume of water to achieve a substantially neutral buoyancy during underwater transport of the item within the submersible transport canister.

Embodiments of a method are further provided for the underwater transport of one or more items utilizing a submersible transport canister of the type that includes a pressure vessel and a diver-adjustable buoyancy system. In one embodiment, the method includes the steps of storing an item within the pressure vessel, and adjusting the buoyancy of the diver-adjustable buoyancy system to impart the submersible transport canister with a substantially neutral buoyancy during underwater transport of the item stored within the pressure vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

At least one example of the present invention will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and:

FIG. 1 is a functional block diagram of a submersible transport canister in accordance with a first exemplary embodiment;

FIGS. 2 and 3 are isometric views of the submersible transport canister shown in FIG. 1 in closed and open positions, respectively;

FIG. 4 is an isometric view of a submersible transport canister in accordance with a further exemplary embodiment;

FIG. 5 is an isometric view of a submersible transport canister in accordance with a still further exemplary embodiment; and

FIG. 6 is an isometric view of a plurality of fixed-volume float collars that can be selectively attached to the submersible transport canister shown in FIG. 5.

DETAILED DESCRIPTION

The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description. As appearing herein, the term “diver” is utilized in a broad sense to encompass any person working within a body of water, whether or not such a person is fully submerged and regardless of the particular manner in which such a person is equipped. Similarly, the term “canister” as appearing herein is defined broadly to include any sealable container, regardless of shape, size, structural features, material composition, etc., suitable for the underwater transport of one or more non-marinized items, as described more fully below.

FIG. 1 is a functional block diagram of a submersible transport canister 10 in accordance with a first exemplary embodiment. Submersible transport canister 10 includes a pressure vessel 12 having an upper open end portion 14, a lower closed end portion 16, and a main storage cavity 18. As generically illustrated in FIG. 1, one or more non-marinized items 20 can be stored within main storage cavity 18 for underwater transport by a civilian or military diver. A non-exhaustive list of non-marinized items that may be stored within main storage cavity 18 includes documents, medical supplies, perishables, electronic devices, and various other commercial-off-the-shelf items. In addition, submersible transport canister 10 is capable of safely transporting lithium ion batteries and other combustible items. The dimensions of storage cavity 18 and, more generally, the dimensions of pressure vessel 12 can be scaled, as appropriate, to accommodate non-marinized items of varying sizes. The geometry of pressure vessel 12 may also be varied, as desired; it is preferred, however, that pressure vessel 12 is generally tubular in shape to optimize the structural integrity of pressure vessel 12 and to facilitate diver transport and storage of submersible transport canister 10 utilizing, for example, a universal boat rack system. Embodiments of submersible transport canister 10 are especially well-suited for utilization by divers and other personnel in the performance of Hurricane Disaster Water Recovery, Boat Accident Recovery, and similar recovery efforts.

FIGS. 2 and 3 are isometric views further illustrating submersible transport canister 10 in closed and open positions, respectively. Referring to FIGS. 2 and 3 in conjunction with FIG. 1, submersible transport canister 10 further includes a watertight cap 22 and a hinge member 24. Hinge member 24 rotatably couples watertight cap 22 to open end portion 14 of pressure vessel 12 and enables the movement of watertight cap 22 between a closed position (FIGS. 1 and 2) and an open position (FIG. 3). In the closed position (FIGS. 1 and 2), watertight cap 22 sealingly engages open end portion 14 to prevent the ingress of water into storage cavity 18 and the wetting of non-marinized items 20 during underwater transport of submersible transport canister 10. In the open position (FIG. 3), watertight cap 22 permits manual access to storage cavity 18 to enable non-marinized items 20 to be inserted into and removed from pressure vessel 12, as desired. Although watertight cap 22 is hingedly coupled to pressure vessel 12 in the illustrated example, this is by no means essential. In further embodiments, watertight cap 22 may be movably attached to pressure vessel utilizing a sliding interface or other non-hinged coupling interface. In still further embodiments, watertight cap 22 may threadably engage open end portion 14 of pressure vessel 12 in the closed position. In this latter case, after inserting non-marinized items 20 into storage cavity 18, the diver may simply screw cap 22 onto open end portion 14 to create a watertight seal prior to underwater transport of submersible transport canister 10.

In embodiments wherein watertight cap 22 does not threadably engage open end portion 14, watertight cap 22 is preferably secured in the closed position (FIGS. 1 and 2) by a latch mechanism or similar structural element to prevent accidental opening during underwater transport of submersible transport canister 10. For example, and as shown most clearly in FIG. 2, watertight cap 22 may be maintained in the closed position by a pull pin 26, such as a cotter pin or a quick release pin. When watertight cap 22 is in the closed position (FIGS. 1 and 2), pull pin 26 extends through an eyelet provided in a first tab 28 projecting from watertight cap 22 (shown in FIGS. 2 and 3) and through an aligning eyelet provided in a second tab 30 projecting from open end portion 14 (also shown in FIGS. 2 and 3). By physically maintaining tab 28 adjacent tab 30, pull pin 26 prevents watertight cap 22 from rotating toward the open position (FIG. 3), and thus secures cap 22 in the closed position (FIGS. 1 and 2), until pull pin 26 is removed by a diver.

One or more seals may be disposed between watertight cap 22 and open end portion 14 of pressure vessel 12 to improve the sealing characteristics of submersible transport canister 10 in the closed position (FIGS. 1 and 2). For example, as generically illustrated in FIG. 1, an O-ring 34 may be disposed around a cylindrical protrusion 32 (also shown in FIG. 3) provided on the underside of watertight cap 22. When watertight cap 22 is in the closed position (FIGS. 1 and 2), O-ring 34 (FIG. 1) is sealingly compressed between the outer circumferential wall of cylindrical protrusion 32 (FIGS. 1 and 3) and an inner circumferential wall of open end portion 14 to provide a watertight seal to a depth of, for example, several hundred feet.

Submersible transport canister 10 further includes a vacuum port 36 and a pressure relief valve 38. Vacuum port 36 and pressure relief valve 38 are each fluidly coupled to main storage cavity 18 of pressure vessel 12. In the exemplary embodiment illustrated in FIGS. 1-3, specifically, pressure relief valve 38 is mounted through a central portion of watertight cap 22, and vacuum port 36 is mounted through the annular wall of pressure vessel 12. Vacuum port 36 is manually accessible from the exterior of submersible transport canister 10 and enables the sealing characteristics of canister 10 to be tested when watertight cap 22 is in the closed position (FIGS. 1 and 2) without actual submersion of canister 10. In particular, a vacuum testing apparatus may be connected to vacuum port 36 and utilized to partially evacuate gas from storage cavity 18 to determine if submersible transport canister 10 remains substantially airtight, and therefore watertight, over a desired pressure range. By comparison, when watertight cap 22 is in the closed position (FIGS. 1 and 2), pressure relief valve 38 vents gas from storage cavity 18 to the exterior of submersible transport canister 10 if the pressure within storage cavity 18 should surpass a predetermined upper threshold due to, for example, combustion of an electrical or chemical component (e.g., a lithium ion battery) contained within cavity 18. In so doing, pressure relief valve 38 prevents the pressure within storage cavity 18 from accumulating to undesirably high levels and, thus, helps render submersible transport canister 10 handsafe when carrying combustible items, such as a lithium ion battery. In one embodiment, vacuum port 36 and pressure relief valve 38 each assume the form of a spring-loaded poppet valve.

Submersible transport canister 10 is further equipped with a diver-adjustable buoyancy system 40 including at least one flotation device, which may be manually adjusted to compensate for the payload weight of non-marinized items 20 (FIG. 1) to impart canister 10 with a substantially neutral buoyancy during underwater transport. In one group of embodiments, diver-adjustable buoyancy system 40 includes an inflatable floatation device that can be inflated to a desired volume by a diver. For example, as indicated in FIGS. 1-3, diver-adjustable buoyancy system 40 can include an inflatable float collar 42, which may be mounted around open end portion 14 of pressure vessel 12. In addition, buoyancy system 40 includes a pressurized cartridge 44, which contains a pressurized gas or gas mixture (e.g., carbon dioxide), and a diver-controllable valve 46, which is fluidly coupled between pressurized cartridge 44 and inflatable float collar 42. Diver-controllable valve 46 normally resides in a closed position in which valve 46 prevents gas flow from pressurized cartridge 44 to inflatable float collar 42. However, prior to usage of submersible transport canister 10, a diver can open diver-controllable valve 46 utilizing a manual control, such as manual control knob 48 to permit gas flow from pressurized cartridge 44, through valve 46, and into inflatable float collar 42. The diver may thus open valve 46 for a sufficient time period to inflate float collar 42 to a volume at which float collar 42, taken in combination with the other components of submersible transport canister 10, displaces a volume of water substantially equivalent in weight to the cumulative weight of submersible transport canister 10 and non-marinized items 20. In this manner, the diver can select the volume of float collar 42 to impart submersible transport canister 10 with a neutral or close-to-neutral buoyancy during underwater transport of items 20 within storage cavity 18. Notably, the diver can adjust and readjust the volume, and therefore the buoyancy, of inflatable float collar 42 in an ad-hoc manner based upon the weight of the item or items to be transported within storage cavity 18.

In embodiments wherein diver-adjustable buoyancy system 40 does not include a pressure gauge, a diver may determine the appropriate volume to which inflatable float collar 42 should be inflated by progressively inflating float collar 42, while submersible transport canister 10 is submerged, until the upward (buoyant) and downward (gravitational) forces exerted on canister 10 are balanced. By comparison, in embodiments wherein diver-adjustable buoyancy system 40 includes a pressure gauge fluidly coupled to float collar 42, the diver can determine appropriate volume to which inflatable float collar 42 should be inflated by simply referring to the pressure gauge. If the pressure gauge includes only pressure markings, the diver may utilize a two-dimensional look-up table to determine the appropriate pressure to which inflatable float collar 42 should be inflated based upon the approximate payload weight of non-marinized items 20. However, in a preferred group of embodiments, the pressure gauge is provided with a read-out (e.g., text) that visually indicates the approximate pressure to which float collar 42 should be inflated to achieve a substantially neutral buoyancy for a range of payload weights. An example of such a neutral buoyancy pressure gauge is described in more detail below.

In the exemplary embodiment illustrated in FIGS. 1-3, and referring specifically to FIG. 1, diver-adjustable buoyancy system 40 further includes a neutral buoyancy pressure gauge 50, which is fluidly coupled between inflatable float collar 42 and diver-controllable valve 46 by way of a bifurcated flow passage 58. Neutral buoyancy pressure gauge 50 includes graphics (e.g., text) that visually indicates the pressure to which inflatable float collar 42 should be inflated to achieve a substantially neutral buoyancy for a range of non-marinized item payload weights. In the illustrated example, the range of payload weights represented on pressure gauge 50 is approximately zero (0) to twenty (20) pounds (graphically indicated in FIG. 1 at 54); however, it will be appreciated that the range of payload weights represented pressure gauge 50 will inevitably vary with the scale of submersible transport canister 10 and various other factors. To impart submersible transport canister 10 with a neutral or close-to-neutral buoyancy during underwater transport of items 20 within storage cavity 18, the diver simply inflates float collar 42 to a pressure at which needle 52 points to the total payload weight of non-marinized items 20. To enable the release of pressurized gas from inflatable float collar 42 should the diver over-inflate float collar 42, a diver-actuated vent valve can be fluidly coupled to inflatable float collar 42, as generically illustrated in FIG. 1 at 56. Neutral buoyancy pressure gauge 50 may comprise either a digital device or an analog device as shown in FIG. 1.

The foregoing has thus provide an exemplary embodiment of a submersible transport canister 10 that can be utilized by a diver to transport non-marinized, commercial-off-the-shelf items, including lithium ion batteries and other combustible items. In the above-described exemplary embodiment, submersible transport canister 10 included a diver-adjustable buoyancy system 40 having an inflatable floatation device (i.e., float collar 42) that can be inflated by a diver utilizing an on-board or integral gas source (e.g., pressurized cartridge 44). The forgoing example notwithstanding, diver-adjustable buoyancy system 40 may not include an on-board gas source in alternative embodiments, and inflation of an inflatable floatation device included within buoyancy system 40 may be effectuated utilizing an external or independent gas source. Further emphasizing this point, FIG. 4 is a functional block diagram illustrating submersible transport canister 10 including a diver-adjustable buoyancy system 60 in accordance with a further exemplary embodiment. As does diver-adjustable buoyancy system 40 described above in conjunction with FIGS. 1-3, diver-adjustable buoyancy system 60 includes an inflatable float collar 42 and a neutral buoyancy pressure gauge 50, which is fluidly coupled to float collar 42 via a bifurcated flow passage 58. However, in contrast to diver-adjustable buoyancy system 40, diver-adjustable buoyancy system 60 further includes a manual fill port 62 and a one-way valve 64, which is fluidly coupled between fill port 62 and inflatable float collar 42. Manual fill port 62 is manually accessible from the exterior of submersible transport canister 10 and enables a diver to inflate float collar 42 utilizing an external gas source, such as a spare oxygen tank carried by the diver, by a surface boat, by a submarine, or by a flooded vehicle. While permitting gas flow from fill port 62 to inflatable float collar 42 to enable inflation of float collar 42, one-way valve 60 prevents gas flow from float collar 42 to fill port 62 to maintain collar 42 in an inflated state.

In the above-described exemplary embodiments of submersible transport canister 10, the diver-adjustable buoyancy system include at least one inflatable floatation device. However, in further embodiments of submersible transport canister 10, the diver-adjustable buoyancy system may include a number of modular, fixed-volume floatation members (e.g., foam or plastic float collars) in lieu of, or in addition to, an inflatable floatation device. FIG. 5 is an isometric view illustrating submersible transport canister 10 equipped with a diver-adjustable buoyancy system 70. Diver-adjustable buoyancy system 70 includes a number of fixed-volume float collars 72, which are illustrated in top plan view in FIG. 6. Fixed-volume float collars 72 each have a substantially annular shape and include a central opening 74 through which pressure vessel 12 may extend as described more fully below. Fixed-volume float collars 72 each have a different predetermined buoyancy. For example, in embodiments wherein fixed-volume float collars 72 each have a substantially uniform density, float collars 72 are each formed to have progressively increasing volumes, as generally shown in FIG. 6.

Prior to usage of submersible transport canister 10, a determines the buoyancy of diver-adjustable buoyancy system 70 by selecting a particular fixed-volume float collar 72 (or float collars 72) based upon the payload weight of non-marinized items 20. In particular, the diver selects a float collar 72 that cooperates with submersible transport canister 10 to displace a volume of water that is generally equivalent in weight to the cumulative weight of canister 10 and non-marinized items 20. To facilitate diver selection of a particular float collar 72, text or other graphics may be provided associating each float collar 72 with a particular payload weight range, as indicated in FIG. 6 at 76. If desired, color coding may also be utilized to further visually distinguish amongst float collars 72. After float collar selection, the diver secures the selected float collar 72 to pressure vessel 12 utilizing, for example, a pin insertion interface of the type described below.

A wide variety of different coupling interfaces can be utilized to enable a diver to removably secure the selected float collar 72 (or float collars 72) to pressure vessel 12. For example, in one embodiment, float collars 72 may each be formed to include an internal threading that engages an external threading provided around upper end portion 14 of pressure vessel 12. As a second example, in the embodiment illustrated in FIG. 5, diver-adjustable buoyancy system 70 includes an annular retention flange 78, which is fixedly mounted (e.g., welded) around upper end portion 14 and which is utilized to secure the selected float collar 72 to pressure vessel 12. Two angularly-spaced apertures 80 are provided through annular retention flange 78 and sized to receive a conventional pull pin 82 (e.g., a cotter pin or a quick release pin) therethrough. Furthermore, as shown in FIG. 6, two angularly-spaced apertures 84 are likewise provided through each float collar 72. To secure a selected float collar 72 to pressure vessel 12, a diver first positions the selected float collar 72 over closed end portion 16 of pressure vessel 12, slides the float collar 72 upward into abutment with retention flange 78 (indicated in FIG. 5 by arrows 86), and then rotates the float collar 72 such that apertures 84 align with apertures 80. Lastly, the diver inserts pull pins 82 through each aperture 80 and its aligning aperture 84 to removably secure float collar 72 to annular retention flange 78 and, therefore, to pressure vessel 12. Notably, due to the disposition and diameter of retention flange 78, float collar 72 will remain in abutment with flange 78 even if pulls pins 82 should be prematurely removed during underwater transport, providing that submersible transport canister 10 is maintained in a generally upright position.

There has thus been provided multiple exemplary embodiments of a submersible transport canister that can be utilized by a diver to transport non-marinized, commercial-off-the-shelf items, including lithium ion batteries and other combustible items. In each of the above-described exemplary embodiments, the submersible transport canister included a diver-adjustable buoyancy system, which can be adjusted by the diver to compensate for the weight of the item or items stored within the canister to achieve a substantially neutral buoyancy and thereby facilitate diver transport of the loaded canister. In view of its ability to transport combustible items, its ability to enable ad-hoc buoyancy adjustments to achieve a neutral or close-to-neutral buoyancy for a range of payload weights, and its scalability, embodiments of the submersible transport canister are well-suited for utilization by divers and other personnel involved in Hurricane Disaster Water Recovery and Boat Accident Recovery.

It should be appreciated that the foregoing has also disclosed embodiments of a method for the underwater transport of an item utilizing a submersible transport canister of the type that includes a pressure vessel and a diver-adjustable buoyancy system. In one embodiment, the method includes the steps of storing an item within the pressure vessel, and adjusting the buoyancy of the diver-adjustable buoyancy system to impart the submersible transport canister with a substantially neutral buoyancy during underwater transport of the item stored within the pressure vessel. In embodiments wherein the diver-adjustable buoyancy system comprises a plurality of fixed-volume floatation members each having a different buoyancy, the step of adjusting the buoyancy of the diver-adjustable buoyancy system may include the sub-steps of selecting a fixed-volume floatation member based, at least in part, upon the weight of the item, and securing the selected fixed volume floatation member to the pressure vessel. In embodiments wherein the diver-adjustable buoyancy system includes an inflatable floatation device coupled to the pressure vessel, the step of adjusting may comprise inflating the floatation device to a volume at which the inflatable floatation device imparts a substantially neutral buoyancy to the submersible transport canister during underwater transport of the item. Finally, in embodiments wherein the diver-adjustable buoyancy system further comprises a neutral buoyancy pressure gauge fluidly coupled to inflatable floatation device and visually indicating the approximate floatation device pressure required to achieve a substantially neutral buoyancy for a given range of payload weights, the step of inflating may comprise: (i) determining the approximate weight of the item, and (ii) inflating the floatation device to a pressure substantially equivalent to the pressure at which the neutral buoyancy pressure gauge indices is required to impart a substantially neutral buoyancy to the submersible transport canister, given the weight of the item.

While at least one exemplary embodiment has been presented in the foregoing Detailed Description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing Detailed Description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set-forth in the appended Claims. 

1. A submersible transport canister, comprising: a pressure vessel having a storage cavity configured to store at least one item therein; a cap movable to a closed position wherein the cap sealingly engages the pressure vessel; and a diver-adjustable buoyancy system configured to be coupled to the pressure vessel and, when so coupled, to displace a volume of water to achieve a substantially neutral buoyancy during underwater transport of the item within the submersible transport canister.
 2. A submersible transport canister according to claim 1 wherein the diver-adjustable buoyancy system comprises a plurality of fixed-volume floatation members each having a different volume and each configured to be removably coupled to the pressure vessel.
 3. A submersible transport canister according to claim 2 wherein the plurality of fixed-volume floatation members comprises a plurality of fixed-volume float collars each configured to be removably mounted around the pressure vessel by a diver.
 4. A submersible transport canister according to claim 3 wherein the diver-adjustable buoyancy system further comprises an annular retention flange provided around the pressure vessel, and wherein each of the plurality of fixed-volume float collars is configured to be removably attached to the annular retention flange.
 5. A submersible transport canister according to claim 3 wherein the submersible transport canister is configured to be utilized in conjunction with a pull pin, and wherein each of the plurality of fixed-volume float collars has an aperture configured to receive the pull pin therethrough to removably secure any selected one of the plurality of fixed-volume float collars to the pressure vessel.
 6. A submersible transport canister according to claim 3 wherein the pressure vessel comprises an open end portion through which the storage cavity is accessible, wherein the cap sealingly engages the open end portion in the closed position, and wherein each of the plurality of fixed-volume float collars is configured to be removably secured around the open end portion.
 7. A submersible transport canister according to claim 1 wherein the diver-adjustable buoyancy system comprises an inflatable floatation device coupled to the pressure vessel.
 8. A submersible transport canister according to claim 7 wherein the inflatable floatation device comprises an inflatable float collar mounted at least partially around the pressure vessel.
 9. A submersible transport canister according to claim 8 wherein the pressure vessel comprises an open end portion through which the storage cavity is accessible, wherein the cap sealingly engages the open end portion in the closed position, and wherein the inflatable float collar is mounted around the open end portion.
 10. A submersible transport canister according to claim 7 wherein the diver-adjustable buoyancy system further comprises a fill port fluidly coupled to the inflatable floatation device and manually accessible from the exterior of the submersible transport canister.
 11. A submersible transport canister according to claim 7 further comprising: a pressurized cartridge fluidly coupled to the inflatable floatation device; and a diver-controllable valve fluidly coupled between the pressurized cartridge and the inflatable floatation device.
 12. A submersible transport canister according to claim 7 further comprising a neutral buoyancy pressure gauge fluidly coupled to the inflatable floatation device, the neutral buoyancy pressure gauge visually indicating, in terms of payload weight, the approximate pressure to inflate the inflatable floatation device to achieve a substantially neutral buoyancy for a range of payload weights.
 13. A submersible transport canister according to claim 1 further comprising a vacuum port fluidly coupled to the storage cavity.
 14. A submersible transport canister according to claim 1 further comprising a pressure relief valve fluidly coupled to the storage cavity.
 15. A submersible transport canister, comprising: a pressure vessel having a storage cavity configured to store at least one item; a cap movable to a closed position wherein the cap sealingly engages the pressure vessel; and a diver-adjustable buoyancy system including at least one flotation device configured to be coupled to the pressure vessel, the diver-adjustable buoyancy system enabling a diver to select the volume of the at least one flotation device such that, when submerged, the submersible transport canister displaces a volume of water generally equivalent in weight to the cumulative weight of the item and the submersible transport canister.
 16. A submersible transport canister according to claim 15 wherein the at least one flotation device comprises a plurality of fixed-volume float collars each having a different buoyancy and each configured to be removably mounted around the pressure vessel.
 17. A submersible transport canister according to claim 15 wherein the at least one flotation device comprises an inflatable float collar mounted around the pressure vessel and configured to be inflated by a diver.
 18. A method for the underwater transport of an item utilizing a submersible transport canister of the type that includes a pressure vessel and a diver-adjustable buoyancy system, the method comprising the step of: storing an item within the pressure vessel; and adjusting the buoyancy of the diver-adjustable buoyancy system to impart the submersible transport canister with a substantially neutral buoyancy during underwater transport of the item within the pressure vessel.
 19. A method according to claim 18 wherein the diver-adjustable buoyancy system comprises a plurality of fixed-volume floatation members each having a different buoyancy, and wherein the step of adjusting comprises: selecting a fixed-volume floatation member based, at least in part, upon the weight of the item; and securing the selected fixed-volume floatation member to the pressure vessel.
 20. A method according to claim 18 wherein the diver-adjustable buoyancy system comprises an inflatable floatation device coupled to the pressure vessel, and wherein the step of adjusting comprises inflating the inflatable floatation device to a volume at which the inflatable floatation device imparts a substantially neutral buoyancy to the submersible transport canister during underwater transport of the item. 